Organic Reserves in ropical Grasses under Grazing

Inadequate management in recent times has been considered the main factor contributing to pasture degradation. A major reason for this is related to gross errors of grazing management as a consequence of the lack of knowledge of ecophysiological limits of forage. This review aimed to approach the importance of organic reserves for grasses under grazing. Therefore, the predominant effect of animal grazing is the reduction of leaf area which impacts on carbohydrate and nitrogen reserves and consequently the growth of tillers, leaves and roots. Grass growth after defoliation is related to organic reserves and rate of photosynthesis. The latter is affected by the level of canopy light interception of and by the reminiscent leaf area index. When grazing management is carried out with respect to the physiological limits of grass growth, the rate of dry matter accumulation will be quick and constant. In this aspect, grazing management consists of seeking an efficient balance between plant growth and consumption which will reflect on animal productivity. Therefore, a balance point among frequency and intensity of defoliation must be found to achieve greater animal production concerning the ecophysiological limits of the forage plants. So the challenge will be to find a balance between frequency and intensity of grazing to achieve greater production of animals respecting the eco-physiological limits of forage plants for each forage grass individually.

Animal Manure as a Nitrogen Source to Grass

The use of animal manure has been studied increasingly in recent years due to the excess waste in confinements, which generates great amounts of animal excreta;and as a result of the worsening petroleum crisis, the cost of mineral fertilizing products has increased. Thus, studies point out the potential of this waste to improve biotic and abiotic soil condition and nutritional value of forage. Substances ingested by animals that resist the action of gastric enzymes are enriched with large amounts of bacteria, other microorganisms and other substances to form residual feces, the main component of manure, which, together with the wash water from barnyard urine, form the slurry. The volume of living or dead bacteria in the feces represents 20% of total manure and it is from these that a large amount of nitrogen originates as protein. Due to this potentiality, animal manure can be used as an input in agriculture, impacting positively on production and forage productivity, and having a favorable effect on the environment.

Structural and Production Characteristics of PiatãGrass Forage Submitted to Levels of Nitrogen

Piat&atilde grass (Brachiaria brizantha cv. Piat&atilde) is a tropical grass cultivating in pasture production system. The aim of this study was to evaluate the effects of nitrogen levels (0, 125, 250, 375 and 500 kg&middotN&middotha-1) on structural characteristics and forage production of Piat&atilde grass. The experiment comprised of twenty grass parcels arranged in randomised completely casualties design. This study was carried out between November of 2007 and April of 2008, with 175 experimental days. A quadratic effect (P &middotm-2 at a nitrogen dose of 357 kg&middotha-1. A quadratic effect (P &middotha-1&middotyear-1?for nitrogen levels of 411 and 384 kg&middotha-1, respectively. However, a considerable portion of forage production obtained by nitrogen addition occurred from stem production. The productions of green leaf blade dry matter, tiller density, leaf blade length and leaf blade index are all variables related to structural aspects and pasture quality, with all attaining their highest values at a mean nitrogen application level of 380 kg&middotha-1.